The idea of using Lithium batteries often scares people, thanks to some bad press caused by the Boeing Dreamliner and “hoverboards” that unexpectedly burst in to flames. Different types of lithium battery behave in different ways. The ones most people use in van conversions are much less volatile, and may even be safer than using lead acid batteries.
Cheap hoverboards (self-balancing scooters) have one thing in common with the Boeing Dreamliner – the same kind of batteries. The Dreamliner batteries that made the headlines in 2012 for catching on fire while in service were LiCoO2 (Lithium Cobalt Oxide) based. This is the same technology used in many of the cheap hoverboards. The Cobalt Oxide batteries can suffer from thermal runaway if they are overcharged, overheated, short circuited, or damaged. They heat up, and overheating produces oxygen from the battery chemicals. This can quickly lead to a fire.
Most of the lithium batteries used in van conversions are Lithium Iron Phosphate (LiFePO4) based. Some may also be Magnesium Oxide (LiMn2O4) based. These types have a slightly lower energy density, but a longer shelf life before they discharge, higher number of charge cycles, and better safety.
This video – made by a Chinese LiFePO4 battery manufacturer – shows the type of abuse the batteries will take. They still off-gas if they are short circuited, and you probably don’t want to be breathing that stuff, but the vapors don’t contain as much oxygen, so they aren’t likely to lead to a fire.
There are still some storage and usage considerations.
- Lithium batteries should not be charged while they are below freezing point. It can cause a build-up of pure lithium metal on the electrodes which permanently damages the battery. Ytterium-doped batteries (LiYFePO4) such as those made by Winston and Balqon may allow charging at lower temperatures, but your mileage may vary.
- LiFePO4 batteries should generally not be used or stored on their sides, because the electrolyte can leak out.
- Different lithium battery types require different protection against expansion. Some need to have their cells strapped together. Others just want the cells to be contained within a metal structure, but not clamped tightly.
- Different lithium batteries also have varying charging profiles. The voltages they want for bulk, absorbtion and float charges will depend from manufacturer to manufacturer. You’ll need to buy a charger that can be programmed to give just the right levels of voltage and current. A generic “lithium” profile may not be right for your battery.
Although each of these cases can lead to battery damage, none are true safety concerns. You can hurt the battery, but it’s less likely to hurt you.
Just in case you think that lead acid batteries are safe, here are some concerns with that technology:
- Charging flooded lead acid batteries produces hydrogen gas, which is highly flammable. They should never be placed inside the living area of the vehicle without proper venting, because the hydrogen can explode.
- Overcharging lead acid batteries will cause them to heat up and potentially boil dry. This is even true for the “sealed” or absorbed glass mat type. The liquid that boils off is highly corrosive.
- Low electrolyte levels can lead to arcing inside the battery, which again can cause hydrogen gas to explode.
- Loose contacts, or ones which have corroded or sulphated through mistreatment can cause arcs. Again, this can make the battery explode. This insurance investigation website talks about checking for embedded fragments of the battery in the walls and ceiling!
- Discharging too rapidly – for instance if the terminals are short circuited – will heat a lead acid battery up considerably. It can heat up to the point where it ruptures and leaks hot acid. That stuff is very corrosive.
There are plenty of other variables that you need to consider when you’re working out whether to use lithium or lead acid batteries in your build, but comparative safety really isn’t one of them.